Real-time control of exhaust flow

ABSTRACT

An interferometric detector detects fluctuations in fluid properties in the vicinity of an exhaust hood to control protective skirts that reduce the exhaust air requirement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No.10/344,505, entitled “Device and Method for Controlling/Balancing FluidFlow-Volume Rate in Flow Channels,” filed Aug. 11, 2003; U.S. patentapplication Ser. No. 10/638,754, entitled “Zone Control of SpaceConditioning Systems with Varied Uses,” filed Aug. 11, 2003,PCT/US03/25515, entitled “Configuration for capture and containmentenhancement of exhaust hood flow by means of jets,” filed Aug. 13, 2003,and U.S. Provisional application 60/590,889, filed Jul. 23, 2004entitled, “Automatic Side Skirt For Exhaust Hood.”

FIELD OF THE INVENTION

The present invention relates generally to flow-volume control devices.More specifically, the present invention relates to flow control devicesthat may be used for balancing fluid flow in a context where suspendedparticles are entrained in the fluid and their precipitation must beavoided, in free-flowing parts of a flow system, except duringfiltration.

Exhaust hoods are used to remove air contaminants close to the source ofgeneration located in a conditioned space. For example, one type ofexhaust hoods, kitchen range hoods, creates suction zones directly aboveranges, fryers, or other sources of air contamination. Exhaust hoodstend to waste energy because they must draw some air out of aconditioned space in order to insure that all the contaminants areremoved. As a result, a perennial problem with exhaust hoods isminimizing the amount of conditioned air required to achieve totalcapture and containment of the contaminant stream.

Referring to FIG. 1, a typical prior art exhaust hood 90 is located overa range 15. The exhaust hood 90 has a recess 55 with at least one vent65 (covered by a filter 60) and an exhaust duct 30 leading to an exhaustsystem (not shown) that draws off contaminated air 45. The vent 65 is anopening in a barrier 35 defining a plenum 37 and a wall of the canopyrecess 55. The exhaust system usually consists of external ductwork andone or more fans that pull air and contaminants out of a building anddischarge them to a treatment facility or into the atmosphere. Therecess 55 of the exhaust hood 90 plays an important role in capturingthe contaminant because heat, as well as particulate and vaporcontamination, are usually produced by the contaminant-producingprocesses. The heat causes its own thermal convection-driven flow orplume 10 which must be captured by the hood within its recess 55 whilethe contaminant is steadily drawn out of the hood. The recess creates abuffer zone to help insure that transient, or fluctuating, surges in theconvection plume do not escape the steady exhaust flow through the vent.The convection-driven flow or plume 10 may form a vortical flow pattern20 due to its momentum and confinement in the hood recess. The Coandaeffect causes the thermal plume 10 to cling to the back wall. Theexhaust rate in all practical applications is such that room air 5 isdrawn off along with the contaminants.

Referring now also to FIG. 2, exhaust hoods 90, such as illustrated inFIG. 1, vary in length and can be manufactured to be very long asillustrated in FIG. 2. Here multiple vents 65 can be seen from astraight-on view from the vantage of a worker 80. The length can presenta problem because the perimeter along which capture and containment mustbe achieved is longer near the ends than in the middle. In the middle,there is only one perimeter, the one along the forward edge indicated at70 in FIG. 1. At the ends, this perimeter includes the side edge as wellwhich is indicated at 75 in FIG. 1. The additional perimeter length thatmust be accommodated at the ends may be called an “end effect.” In otherwords, the hood cannot be approximated as a two-dimensionalconfiguration because of its finite length. As a result of the increasedperimeter at the ends, more air must be exhausted in the vicinity of theends of the hood than in the middle because the perimeter at the endsconsists of both the forward edge 70 of the hood adjacent the worker andend edges 75, which are perpendicular to the forward edge 70.

If the minimum exhaust rate for the entire hood is to be achieved, thenless air should be exhausted near the middle section than near the ends.Otherwise, an excess rate of air exhaust will occur near the middlesection to insure the rate at the ends is sufficient. Thus, as a resultof the end effects and the requirement of full capture and containment,more air must be drawn through the middle section than necessary. Inaddition, a higher volume of effluent may be generated at some parts ofa hood than at others. This variability leads to the same result: someparts of the hood may require a greater exhaust rate than others.

Referring to FIG. 3, a similar problem occurs when multiple hoods areconnected to a single exhaust system. For example, the hoods may beconnected to a common exhaust duct 191. Each hood must be balancedagainst the others so that each exhausts at the minimum rate thatensures full capture and containment of the contaminants. Again, ductscarrying grease aerosol should not have dampers because of the hazardcaused by grease precipitation.

The particular embodiments are presented in the cause of providing whatis believed to be the most useful and readily understood description ofthe principles and conceptual aspects of the invention. In this regard,no attempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention. The description, taken with the drawings, makes it apparentto those skilled in the art how the several forms of the invention maybe embodied in practice.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a side view of a canopy style wall hood according to the priorart.

FIG. 2 is a front view of a long canopy style hood with multiple vents.

FIG. 3 is a front view of multiple hoods attached to a common exhaustsystem.

FIG. 4 is a side section view of a canopy style hood according toembodiment of the invention.

FIG. 5A. is a section view of a canopy style hood according to theembodiment of FIG. 4.

FIG. 5B. is a perspective view of a shutter with an actuator mechanismaccording to embodiment of the invention.

FIG. 6 is a front view of a canopy style hood with multiple ventsincluding the shutter mechanism of FIG. 5B.

FIG. 7 is a front view of multiple canopy style hoods connected to acommon exhaust in which respective vents of the hoods are controlled byshutter mechanisms according to embodiment of the invention.

FIG. 8 is a section view of a canopy hood with a shutter according toanother embodiment of the invention.

FIG. 9A is a side view of a centrifugal style cartridge filter used forgrease extraction.

FIG. 9B. is a section view of a canopy style hood with a flow controlmechanism according to another embodiment of the invention.

FIG. 10 is a side view of a canopy style hood with the flow.degree.control mechanism according to still another embodiment of theinvention.

FIG. 11 is a front view of vents of a canopy hood or back shelf hoodwith rolling shutters according to yet another embodiment of theinvention.

FIG. 12 is a section view of rolling shutter mechanism according to anembodiment of the invention.

FIG. 13 is a partial section view all long hood with multiple exhaustvents and corresponding flow of throttling devices according to anembodiment of the invention.

FIG. 14 is a sectional side view of the embodiment of FIG. 13.

FIG. 15 is the perspective cut away of a shutter mechanism according toembodiment of the invention.

FIG. 16 a perspective cut away of a shutter mechanism according toanother embodiment of the invention.

FIG. 17 is a sectional view of a combination filter/flow throttlingdevice according to embodiment of the invention.

FIG. 18 is a sectional view of a combination filter/flow throttlingdevice according to embodiment of the invention.

FIG. 19 is a sectional view of a combination filter/flow throttlingdevice of FIG. 18 in a throttle-down position.

FIG. 20 is the face view of the filter of FIGS. 18 and 19 shown partlyin throttle-down position and partly in throttle-up position.

FIG. 21A is a sectional view of a combination filter/flow throttlingdevice according to yet another embodiment of the invention.

FIG. 21B. is a sectional view of the filter/flow throttling device ofFIG. 21 a in the throttle-up position.

FIG. 21C. is a front view of the filter of FIGS. 21 a and 21B.

FIG. 22A is a section view of a filter/flow throttling device accordingto another embodiment of the invention.

FIG. 22B. FIG. 22B is a section view of the filter of FIG. 22A in athrottle-down position.

FIG. 22C is a front view of the filter of FIGS. 22A. and 22B.

FIG. 23A is a alternative embodiment of the device of FIGS. 22A throughc.

FIG. 23B. is an alternative embodiment of the device of FIGS. 22 athrough 22C.

FIG. 24A. is a section view of a canopy hood with a flow throttlingdevice including a cleaning fluid according to embodiment of theinvention.

FIG. 24B. is a section view of the flow throttling device of FIG. 24 dayin the throttle-down position.

FIG. 24C. is a top view of the embodiments of FIGS. 24A and 24B.

FIG. 25A is a section view of a flow throttling device also using Acleaning fluid according to embodiment of the invention.

FIG. 25B is a section view of the flow throttling device of FIG. 25 a ina throttle-down position.

FIG. 26 is a section view of a canopy hood showing a flow throttlingdevice in which apply them is contracted according to embodiment of theinvention.

FIG. 27 is a section view of the embodiment of FIG. 26 in throttle-downposition.

FIG. 28 a business section view of the canopy hood showing a flowthrottling device employing an expandable bladder according toembodiment of the invention.

FIG. 28B is a section view of the flow throttling device of FIG. 28 a inthrottle-down position

FIG. 29 to section view of a canopy hood with a flow throttling deviceemploying a flexible back wall of a plenum according to embodiment ofthe invention.

FIG. 30 is a section view of a canopy hood with a flow throttling deviceusing a ball bowel arrangement according to embodiment of the invention.

FIG. 31 is a section view of a canopy hood with the flow throttlingdevice of FIG. 30 in throttle-down position.

FIGS. 32A and 32B are side views of an alternative bowel arrangementsuitable for use in the embodiment of FIGS. 30 and 31.

FIG. 33 is a section view of a flow throttling device for a hood and athrottle-up position according to an embodiment of the invention.

FIG. 34 is a section view of the flow throttling device of FIG. 33 in athrottle-down position.

FIG. 35 is a front view all long hood with multiple vents and multipleduct sections which may be selectively blocked according to embodimentof the invention.

FIG. 36 is a section side view of the embodiment of FIG. 35.

FIG. 37 is a perspective view of a cylindrical module of a combinationfilter/flow throttling device according to an embodiment of theinvention.

FIG. 38 is a perspective view of a combination filter/flow throttlingdevice employing the module of FIG. 37 and a rotating assembly.

FIG. 39 is a perspective view of the embodiment of FIG. 38 and athrottle-up position.

FIG. 40 is a section view of a canopy style hood sensors to gather dataabout cooking conditions.

FIG. 41 is a blocked side man of the controller with sensors forcontrolling the balance of one or more kitchen exhaust hoods.

FIG. 42 is a perspective view of a cooking appliance and hood showingvarious camera angles.

FIG. 43A is a side view of a hood and cooking appliance with a plume inwhich the exhaust rate is higher than necessary.

FIG. 43B is a side view of a hood and cooking appliance with a plume inwhich the exhaust rate is set at an optimal rate.

FIG. 43C is a side view of a hood and cooking appliance with a plume inwhich the exhaust rate is set to low.

FIG. 44 is a perspective view of a canopy quoted and cooking applianceshowing a plume escaping containment.

FIG. 45 is a Schlerian photograph of the thermal plume rising from acooking appliance into a canopy hood.

FIG. 46 is a section view of a canopy hood with a shutter and anactuator mechanism according to embodiment of the invention.

FIG. 47 is a section view of a canopy hood with a shutter and anactuator mechanism according to another embodiment of the invention.

FIG. 48A is a perspective view of expandable scroll module whichfunctions as a filter/flow throttling mechanism according to anembodiment of the invention.

FIG. 48B is a perspective view of a set of the expandable scroll modulesof FIG. 48A attached to each other such that they can expand andcontract as a unit.

FIG. 49 is a section view of the embodiment of FIG. 48 in a throttle-upposition.

FIG. 50 is a section view of the embodiment of FIGS. 48 and 49 in athrottle-up position.

FIG. 51 is a perspective view of the embodiment of FIG. 48 showing asupporting framework and actuator mechanism.

FIG. 52 is a section view of the embodiment of FIG. 51 showing a supportfeature of that embodiment.

FIG. 53 is a perspective view of an embodiment similar to the embodimentof FIGS. 48A and 48B in which flow exits from a central position betweendivided sets of scroll modules.

FIG. 54 shows a support structure for the embodiment of FIG. 53.

FIG. 55 is a side view illustration of a canopy style hood withadjustable side skirts according to a first inventive embodiment.

FIG. 56 is a schematic illustration of a control system for theembodiment of FIG. 3A as well as other embodiments.

FIG. 57 is a side view illustration of a backshelf hood with a fire gapand movable side skirts and a movable back skirt.

FIG. 58 is a side view illustration of a canopy style hood withadjustable side skirts according to a second inventive embodiment.

FIG. 59 is a figurative representation of a combination of horizontaland vertical jets to be generated at the edge of a hood according to aninventive embodiment.

FIG. 60 is a figurative illustration of a plenum configured to generatethe vertical and horizontal jets with diagonal horizontal jets at endsof the plenum according to an inventive embodiment.

FIG. 61 is an illustration of a plan view of a typical hood showing acentral location of the exhaust vent.

FIGS. 62A and 62B illustrate the position of the plenum of FIG. 7 aswould be installed in a wall-type (backshelf) hood as well as acombination of the horizontal and vertical jets with side skirtsaccording to at least one inventive embodiment.

FIGS. 63A-63C illustrate various ways of wrapping a series of horizontaljets around a corner to avoid end effects according to inventiveembodiment(s).

FIG. 63D illustrates a way of creating a hole in a plenum that redirectsa small jet without a separate fixture by warping the wall of theplenum.

FIG. 64A illustrates a canopy-style hood with vertical jets and aconfiguration that provides a vertical flow pattern that is subject toan end effects problem.

FIGS. 64B and 64C illustrate configurations of a canopy hood that reduceor eliminate the end effect problem of the configuration of FIG. 10.

FIG. 64D illustrates a corner shield configuration for a hood withcurtain jets.

FIG. 65A illustrates an application for a breach detector for a hoodcontrol system.

FIG. 65B illustrates an interferometer sensor and a detectorconditioning circuit for various embodiments of interferometer-basedsensing of fume breach.

FIG. 65C illustrates an interferometer using a directional coupler andoptical waveguides instead of beam splitter and mirrors.

FIG. 65D illustrates some mechanical issues concerning measurements thatdepend on the structure of turbulence.

FIG. 66 illustrates a combination make-up air discharge register andhood combination with a control mechanism for apportioning flow betweenroom-mixing discharge and short-circuit discharge flows.

FIG. 67 illustrates a combination make-up air discharge register andhood combination with a control mechanism for apportioning flow betweenroom-mixing discharge and a direct discharge into the exhaust zone ofthe hood from either outdoor air, transfer air from another conditionedspace, or a mixture thereof.

FIGS. 68A and 68B illustrate drop-down skirts that can be manually swungout of the way and permitted to drop into place after a time interval.

FIG. 69 illustrates a control system for the device of FIGS. 68A and68B.

FIG. 70 illustrates an embodiment of a device consistent with thedescription of FIGS. 68A and 68B.

FIG. 71 illustrates a multisensor configuration of an interferencedetector.

FIG. 72 illustrates another view of the multisensor configuration ofFIG. 71 showing installation on a hood.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following US patent applications are hereby incorporated byreference as if set forth in their entireties herein: U.S. patentapplication Ser. No. 10/344,505, entitled “Device and Method forControlling/Balancing Fluid Flow-Volume Rate in Flow Channels,” filedAug. 11, 2003; U.S. Pat. No. 6,851,421, entitled “Exhaust Hood with AirCurtain to Enhance Capture and Containment,” and U.S. patent applicationSer. No. 10/638,754, entitled “Zone Control of Space ConditioningSystems with Varied Uses,” filed Aug. 11, 2003.

Referring to FIG. 4, a kitchen hood 125 has a canopy 145 positioned overa heat/contaminant source 175 (such as a grill) to capture a thermalconvection plume 170 produced by the heat/contaminant source 175. Thecanopy 145 defines a recess 140, having an access 155. An exhaust fan(not shown) draws a flue stream 105 through an exhaust plenum 180.Negative pressure in the exhaust duct 180 in turn draws gases residingin the recess 140 through a vent 130. In the vent 130 is a mechanicalgrease filter 115, set in a boundary wall 120 that defines part of therecess 140. The filter reduces the mass of suspended grease particles inthe resulting flue stream. The grease filter 115 may be an impingementfilter or one based on cyclone type separation principles. The thermalconvection plume 170 carries pollutants and air upwardly into the canopyrecess 140 by buoyancy forces combined with forced convection resultingfrom the suction created by the exhaust fan. A combined effluent streamcomprising the thermal convection plume 170 and conditioned air drawnfrom the space 165 in which the hood 125 is located, flows into thevortex 135. This flow is extracted from the canopy recess 140 steadilyforming the effluent stream 110, which becomes the flue stream 105.

The kitchen hood 125 may have multiple vents 130, each connected to theexhaust plenum 180. Alternatively, multiple exhaust plenums 180 may beconnected to a single exhaust duct header (not shown but as indicated at191 in FIG. 3) supplied by a single fan (not shown) as will beappreciated by those skilled in the relevant art. The exhaust ratethrough the exhaust plenum 180 or exhaust duct header determines therate of extraction of effluent and indoor air 165 by the hood 125. Thedetermination of the optimal flow rate involves a tradeoff betweenenergy conservation and a requirement called capture and containment.Capture and containment is the state where no pollutant from the thermalplume 170 or the buffered volume in vortex 135 escapes into theconditional space.

Full capture and containment requires the exhaust of at least some air165 from the space in which the hood 125 is located. To conserve energy,the exhaust rate should be set at the lowest possible rate that stillprovides full capture and containment. This setting must account for thevariability of the thermal plume 170, which varies with the cookingload, stage of cooking (e.g., rendering of fat which causes dripping andattendant smoke), and random variation (e.g., random dripping from fattyfoods) or steam generation. Thus, not only does the exhaust load varyalong the canopy 125 (in the direction into the plane of the drawing),as discussed in the background section, it also varies with time. Theprior art approach has been one of setting the flow rate according tothe peak expected load. This approach insures that the bulk exhaust rateis high enough to provide full capture and containment by the hood, orhood portion, requiring the greatest volume of exhaust to achieve it(capture and containment), at the times of maximum instantaneous load.

Again, the load can vary along the length of a long hood or from hood tohood and the balancing problem is analogous in balancing from hoodportion to hood portion as it is for balancing from hood to hood.

In the present system, a flow control system is employed to permitmodulation of the exhaust from one hood 125 to another or from one vent120 to another along a single long hood 110. In addition, the potentialexists to provide this flow control system, to be discussed hereon, withreal-time control. Thus, according to the inventive system, the exhaustrate. may be controlled to achieve the lowest local (“local” referringgenerically to the respective hood portion or the respective each hoodlinked to a common exhaust) exhaust rate required for the current local,instantaneous load. This is achieved by controlling the local exhaustrate by an active flow control device 120 linked to a real-time control(discussed in greater detail much later in the present specification).

Referring now also to FIGS. 5A, 5B, and 6, to balance flow across asingle hood 145 (FIG. 6), or across multiple hoods connected to a singleexhaust system (see FIG. 7), a flow control device 120 selectivelyblocks a portion of an exhaust vent 130 in a boundary wall 190 of thehood 145. The flow control device 120 has a flat plate 112 partiallycovering the vent 130 defining an aperture 185. The flat plate 112 isselectively moved across the vent 130 which makes the aperture 185variable-sized. The flat plate 112 may be moved by a linear actuator 119such as a linear motor with a driver 118 and stator 117. The flat plate112 may be guided by linear bearings 113. Note that the shape of theflow control device 120 is generally flat so that its impact on theshape of the canopy recess 140 is minimal. Thus, the flow control device120 does not interfere with the vortical flow pattern 135. Where canopy145 is of great length (again, “length” referring to the dimensionperpendicular to the plane of the FIG. 5A drawing and best illustratedby FIG. 6), where multiple vents 130 are linked to a common exhaust duct205, the respective flow control devices 120 may be set to provide alarger aperture 185 for the vents 130 close to the ends of the canopy145 and to provide a smaller aperture 185 for the vents 130 near themiddle of the canopy 145. Alternatively, if the type of cookingappliance or load varies along the length of the hood, the flow controldevices 120 may be set accordingly. Referring now also to FIG. 7, inmultiple hoods 230 linked to a common exhaust header 220 the flowcontrol device 120 may be set to restrict flow more in those canopies145 protecting lower loads and to restrict flow less in canopies 145protecting higher loads. Further, real-time control, which is discussedlater in the present specification, may be used to control each flowcontrol device 120 according to an instantaneous load sensed by a smoke,temperature, image, and/or other sensor system as described below.

Referring to FIG. 8, the canopy recess 140 acts as a buffer to dampenthe effects of temporal variability in the load. The thermal plume 170rises at a rate that is faster than the mean rate of exhaust. Inwall-type hoods as illustrated, the flow 135 circulates within thecanopy recess 140 dissipating its energy in a turbulent cascade whilstthe plume 170 and room air 165, drawn by negative pressure created bythe exhaust fan (not shown), are tapped from the canopy recess 140 asindicated figuratively by the arrow 245. The shape of the canopy recess140 augments the vortical pattern by guiding it in a circular path asillustrated at 135. The vortical pattern may not be present in allhoods, but all hoods have some capacity to buffer temporal variabilityin the load whether a stable vortex is formed or not. More complex flowpatterns may arise in other hoods, depending on the load, the hood shapeand other variables.

Referring now to FIGS. 9A, 9B, and 10, another type of flow controldevice provides variable control of the flow rate through certain typesof filters 305. Referring momentarily to FIG. 9A in particular, incertain types of filters 305, the raw effluent stream enters asindicated at 246 and leaves at the ends of the filters as indicated at307. Examples of this type of filter are described in U.S. Pat. No.4,872,892, which is hereby incorporated by reference in its entirety asif fully set forth herein. Focussing again on FIG. 9B, the exit flows307 are selectively blocked by movable plates 300 thereby providing avariable exit passage 325. In the embodiment of 9B, the plates 300translate as indicated by arrows 308. In the embodiment of FIG. 10,movable plates 330 are pivotably mounted by hinges 335 and pivoted toprovide variable exit passages 340.

Referring now to FIGS. 11 and 12, another embodiment of a flow controldevice employs scroll shutters 360 that unroll from spools 385 inside acovered compartment 265. Each shutter 360 selectively blocks a vent 370on the canopy recess side thereby providing a variable aperture 350respective of each vent 370. Each vent 370 may be separated by apartition portion 380 from one or two adjacent vents 370. Suitableguides and drive mechanisms are available from the field of movableshutters and may be employed to actuate the present embodiment.

Referring to FIGS. 13 and 14, a flow control device such as described inU.S. Patent Application 60/226,953 may be employed in a duct leadingfrom the respective vents 420 of a single hood or from groups of ventsin one or more hoods all linked to a common exhaust (not shown in thisdrawing). In the embodiment of FIGS. 13 and 14, a single hood is shown.A wall 425 of the recess has three vents 420 each leading to arespective plenum 430. Each plenum is connected to a duct containing aflow control device 410 having smooth walls as described in the above USpatent application. Each flow control device 410 then leads to a commonplenum 400 from which effluent is drawn through a common exhaust 415. Byregulating each flow control device 410 separately, the flow through therespective vents 420 can be optimized as discussed above. A similarconfiguration may be used to balance respective hoods connected to acommon exhaust.

Referring to FIG. 15, another type of flow control device 510selectively blocks flow through a vent 505 (in a wall of a canopy 525)using a vertical-blind type mechanism. Louvers 515 of the flow controldevice 510 pivot in a manner analogous to window blinds. The louvers 515may be oriented with their pivot axes parallel to the tangent of thevortex 135 formed within a canopy recess 500. In this orientation, thelouvers 515 generate less resistance to the vortical flow. To vary theflow through the flow control device 510, the louvers 515 are pivotedabout their axes in concert to vary the net flow area through the vent505 in the canopy wall 525. Referring to FIG. 16, in flow control device530, which is similar to that of FIG. 15, louvers 535 are located overonly a portion of the vent 505, since the flow may not need to be cutoff 100%. Alternatively, the louvers 515 may be as in FIG. 15, but notclose 100%.

Referring to FIG. 17, the structure of an impingement filter 545 isvaried to modulate flow therethrough. The drawing shows a split view ofa single filter in two configurations. On the left side of the drawing,the concave-back plates 550 and concave forward plates 555 are closetogether narrowing the flow passage between the inlets 570 and theoutlets 580. In the right side of the drawing, the separation distanceis increase providing a larger flow passage that is correspondingly lessresistant to flow therethrough. The separation distance may be variedprogressively or step-wise, depending on design choice, by any suitablemechanism.

In the example shown, adjustable standoffs 560 are used to separate theplates 550 and 555. For example, the adjustable standoffs could bescrews 560 with idle clips 565 that hold one end of the screws 560 at afixed position along it length and threaded holes 566 that traverse thelengths of the screws 560 when it is turned. The separation device maybe automatic or manual, as required.

Referring to FIGS. 18, 19, and 20, in a configuration of a grease filterof a type similar to those described in U.S. Pat. No. 4,872,892,modulation of the flow of exhaust through a vent of a range hood isafforded. In this embodiment, a filter is formed substantially asdescribed in the above patent. That is, air flows into slots 620 along aface of the filter as indicated at 632 (all similar slots—only one islabeled) and exits through the ends of tubular sections 610 as indicatedby the outward-facing-flow symbol 633. While travelling through eachchamber tubular section 615, the flow swirls helically due to thetangential entry of the flow at each slot 620. The aperture of the slots620 is varied by bending a flexible wall 630 of each slot by a gangpull-rod 635. When the gang pull-rod is moved as illustrated in FIG. 19,the flexible walls 630 bend narrowing the slots 620 and restricting theflow. FIG. 20 is a split view showing two configurations of the filter.The open configuration of FIG. 18 is illustrated on the left side ofFIG. 20 and the closed configuration of FIG. 19 is illustrated on theright side of FIG. 20. The aperture 620 may be varied progressively orin steps.

Note that while in the embodiment of FIGS. 18-20, the inlet slots 620are varied in flow area by bending a wall that forms the tubularchambers 615, it is possible to accomplish a similar result usingseparate blocking plate with a hinge. That is, the wall 630 may be aseparate element pivotably attached to the rest of the modules 610.

Referring to FIGS. 21A, 21B, and 21C, based on a filter design similarto those of U.S. Pat. No. 4,872,892, flow entering the filter isselectively blocked by a movable shutter plate 660. Again each tubularchamber 650 receives air through a respective slot-shaped flow aperture655 and delivers it through exits 649 of each of a plurality of modules648 as indicated by the arrows 656 and 657. When the shutter plate 660is in a relatively open position as shown in FIG. 21A, each flowaperture 655 is relatively large in area. When the shutter plate 660 isin a relatively closed position as shown in FIG. 21B, the flow aperture655 is relatively small in area. Thus, the shutter plate 660 positionmay be used to control the pressure drop across the filter andconsequently the flow rate across the filter.

All of the filters that are able to control flow may be used for hoodbalancing. If each filter is controlled independently, the flow ratethrough each vent of one or more hoods can be controlled independently.Each filter may be controlled in each hood of a system to flow-balancelonger hoods and to balance hoods against each other. Alternatively, asingle filter of a hood with multiple vents can be controlled leavingthe other filters uncontrolled. This may allow the balancing of theentire hood against other hoods. In a longer hood, this solution may beless desirable because it would vary the exhaust rate across the lengthof the hood, which may produce inefficiencies as discussed above.

Referring to FIGS. 22A, 22B, and 22C, based on a more conventional typeof filter cartridge known as an impingement filter (also discussedabove), a shutter plate 653 is moved to vary the size of flow apertures657. Effluent flows from the inlet flow apertures 657 to respectiveoutlets 658. The selective variation of the flow apertures 657 variesthe pressure drop through the flow apertures 657. Note that although inthis embodiment, a shutter plate 653 is used to selectively block theaperture 657, it is clearly possible to use a shutter plate toselectively block the outlets 658 or both to achieve the same effect.

The shutter plate of FIGS. 21A-C and 22A-C are illustrated as havingrectangular openings. Referring to FIGS. 23A and 23B, it is possible toemploy other shapes to good effect. For example, in the embodiment ofFIG. 23A, a shutter plate 680 has openings 675 with a curved border suchthat access to the middle section of the filter is blocked more than theends. In the embodiment of FIG. 23B, the opposite is true. In the latterembodiment, a shutter plate 681 has openings 676 with a curved bordersuch that access to the end sections is blocked more than the middlesection. Either embodiment may be used with either type of filtercartridge or others not described herein, but the embodiment of FIG. 23Bmay be more favorable in a filter such as described in U.S. Pat. No.4,872,892 because it favors a longer travel path of the air along theflow modules providing greater grease separation in the process.

Referring to FIGS. 24A and 24B, a canopy 717 has a recess 715 bounded,in part, by a flexible accordion wall 710, a filter 720, and a watertank 730. The filter 720 is partly immersed in a pool of water or otherliquid 735, held by the tank 730. The exposed face of the filter islimited by the immersion of part of the filter 720 in the pool of water735 and thus the flow area is reduced. As a result, the flow area may bemodulated by varying how deeply the filter 720 is immersed. By varyingthis flow area, the pressure drop between the recess 715 and a plenum725 may be selectively varied to vary the exhaust flow. To vary thedepth of immersion, the filter 720 may be translated. The flexibleaccordion wall 710 flexes to follow the filter 720. The flexibleaccordion wall 710 may be made of steel or some other material. Thefilter may be held by a suitable engagement device (not shown) at thedistal end of the flexible accordion wall 710. Cleaning solution may beused in the tank 730. During shutdown of the exhaust system, the filter720 may be immersed more completely in the cleaning solution to cleanthe filter 720.

Referring now also to FIG. 24C, seal plates 723 prevent effluent gasesfrom bypassing the filter 720 by going around it. The seal plates mayextend from the top of the accordion wall 710 to the level of the liquid735.

Referring now to FIGS. 25A and 25B, in another embodiment, a recess 745is bounded in part by a fixed wall section 740 to which a filter 750 isconnected at a distal end thereof. Seal plates (not shown) may beprovided as in the embodiment of FIGS. 24A-24C. The filter is immersedpartly in a tank 755 filled with water or a cleaning solution or someother liquid 760. Pressure drop between a suction-side plenum 765 andthe recess 745 across the filter is governed by the level of the liquid760 in the tank 755 which in turn controls the flow area availablethrough the filter. In FIG. 25A, the flow area is greater than theillustration of FIG. 25B because the liquid 760 level is higher in thelatter figure.

Referring now to FIGS. 26 and 27, a recess 788 of an exhaust hood 789 isdefined in part by a pivoting wall 781 that pivots at one end 790 and isconnected by a flexible wall 781 at another end. The pivoting wall 781also defines in part a suction side plenum 775 whose flow passage isreduced in flow area by the change in the angle of pivot of the pivotingwall 781. The flow through each controlled vent 786 may be modulated bymeans of an independent apparatus as shown. Thus, for balancing flowthrough a single hood, two or more sets (“sets” may be single in number)of vents may lead into separately controlled plenums 775.

Referring to FIGS. 28A and 28B, a hood canopy 815 has a plenum 810 thatreceives exhaust air through a filter 820. The pressure drop through theplenum 810 is modulated by varying the configuration of an obstruction805. The obstruction may, for example, be an inflatable bladder. Theobstruction may be made of steel with an accordion type bellow integralthereto to permit its volume to vary. Alternatively, it may be ofpolymeric material or other suitable construction. The obstruction 805is shown with a substantially pillow shape, but it is understood that itcould have any shape. A shape that presents a face that is substantiallyparallel to the exit face of the filter 820 would be better than onethat is at a substantial angle as shown so as not to favor one portionof the filter over another. Referring to FIG. 29, in a variation of theembodiments of FIGS. 28A and 28B, wall of the plenum 810 has a face 808and accordion ribbing 807 to permit the face 808 to be pushed into theplenum 812 to vary the flow channel area and thereby the pressure dropthrough the plenum. The same effect would be accomplished with anobstruction as in FIGS. 28A and 28B. That is, the face angled as face808 could be formed in the obstruction 805.

In the embodiments of FIGS. 28A, 28B, and 29 separate plenums 810/812may be provided for each modulated vent 814/811. Alternatively, however,because the flow obstructor 805/808 may be made local to a respectivevent 814/811, all vents may share a common plenum 810/812 for a singlehood while still providing the ability to balance a single long hood.That is, a separate and independently controllable flow obstructor805/808 may be made respective to each vent 814/811 to control eachcontrolled vent independently of the others.

Referring to FIGS. 30 and 31, a hood of substantially standardconstruction has a suction side plenum 835 which draws air through afilter 820. An aperture 832 leads to an exhaust collar 800. The aperture832 is selectively blocked by a smooth obstruction 830 whose distancefrom the aperture 832 determines the flow area for exhaust flow throughthe aperture. In an embodiment, the flow obstruction 830 is in the shapeof a sphere. Referring to FIGS. 32A and 32B, an alternative shape for aflow obstruction 840 is a water-drop shape. For rectangular flowapertures 832, other shapes may be used. Preferably, the shape of theflow obstruction is smooth so as not to generate stable and quasi-stableor periodic flow structures that result in undue precipitation ofaerosols.

Referring to FIGS. 33 and 34, in a rectangular exhaust collar 850 fedfrom a suction side plenum 860 of an exhaust hood, flexible smooth flowobstructor plates 855 are provided. By varying the shape and area of aflow channel 857, the pressure drop across the flow channel 857 ismodulated providing the ability to balance suction side plenums 860selectively. The shapes' of the obstructor plates 855 may be varied bytranslating tongue segments 856 accordingly. The final actuator used tovary the shape and size of the flow channel 857 may be any suitabledevice. Note that one side only may be translated rather than both asindicated.

Referring to FIGS. 35 and 36, an exhaust hood has a suction side plenum535A divided into an upper part 535A and a lower part 535B. The upperand lower parts 535A and 535B are connected by a series of duct sections547/548 that may be selectively covered with blanks 546 to vary the flowthrough each respective vent 566. In the example situation shown in FIG.35, two of the middle-most blanks are set to block flow through ducts547 and permit free flow through ducts 548. By selectively blocking someducts 547 and permitting flow through other ducts 548, the relative flowof the vents 566 is altered. For example, the flow through vent 566′would be reduced relative to the flow through adjacent vents 566 becauseof the presence of the blanks 546. Since no obstructions are added to aflow path, no mechanism is introduced that would cause undueprecipitation.

Note that while in the embodiment of FIGS. 35 and 36, the blanks 546 arefixed in place, it would be possible to arrange for the blanks 546 to beselectively moved into place to provide real-time modulation of flow.Thus, in this embodiment, a movable blank 546 would either be in placeblocking flow through a respective duct section 547 or it would be outof the way permitting free flow through the respective duct section 548.Also, while in the embodiment described above, it was presumed that theconfiguration of the plenum 535B was such that flow through the middlevent 566′ would be appreciably reduced relative to that through theother vents 566, the latter plenum may be sufficiently generously sizedthat the only effect of reducing the aggregate flow area by blockingducts 547 may be to reduce the total flow for the entire hood withoutredistributing the flow along the hood. Thus, this design may be used tobalance multiple hoods or single hoods, as may all the previousembodiments. The advantage of using this technique rather than a singleflow control, however, is that it does not create any obstruction aroundwhich fumes and air must flow. Thus, it avoids the attendingprecipitation problems.

Referring to FIG. 37, a cylindrical grease filter module 580 has ininlet 588 through which raw effluent and air are drawn and an outlet 592from which the cleansed air is extracted. A guide van 582 causes anincoming stream 584 to be directed into a helical flow 590 so thatgrease and other airborne particulates precipitate on its interiorwalls. The exit flow 586 is directed at approximately a right angle tothe incoming stream 584. Functionally, the cylindrical grease filtermodule is similar in function to that of the filters described in U.S.Pat. No. 4,872,892. Its cylindrical walls, however, may provide lowerresistance and improved cyclonic flow therewithin.

Referring to FIGS. 38 and 39, a filter cartridge 581 is formed frommultiple cylindrical grease filter modules 580. Each cylindrical greasefilter module has a lever tab 604 which is tied to a rotator bar 602which is used to rotate the cylindrical grease filter modules 580 inconcert. By rotating the cylindrical grease filter modules 580, theexposed area of the inlet 588 of each cylindrical grease filter module580 is selectively altered. When the cylindrical grease filter modules580 are in the positions shown in FIG. 38 the flow through the filtercartridge 581 is restricted more than when they are in the positionsshown in FIG. 39. This is because the inlets 588 are increasinglyblocked by partitions 606 as the cylindrical grease filter modules 580rotate clockwise. Note that in an alternative embodiment, thecylindrical grease filter modules 580 may be set immediately adjacent toeach other and the blocking function of the partition plate formed bythe external surfaces of adjacent cylindrical grease filter modules 580.In this way, the partition plates 606 may be avoided.

Referring to FIGS. 40 and 41, various sensor mechanisms may be used toprovide real time control of the flow rate through one or more hoods.For example, a controller 950 may receive input signals from one or moreinput devices including one or more video cameras 961, infrared videocameras 962, opacity sensors 963, temperature sensors 964, audiotransducers 965 (e.g., microphones), manual switches 966, and flow ratesensors 967. Based on one or more of these inputs signals the controllermay control the setting of one or more output controllers 970 connectedto any of the flow control devices described previously or describedlater in the present specification. Video or IR cameras may be locatedat any desired position, examples being indicated at 920 and 935 and asdiscussed later in connection with FIG. 42. Opacity and temperaturesensors may be located at any positions, two examples being indicated at925/930.

The technology in image processing is more than adequate to detect achange in a volume of smoke or heat resulting from an increased cookingload. Optical and/or infrared images may be captured and a cooking loadindicator derived therefrom. For example, an IR image processingalgorithm that simply indicates the percentage of the field of view thatis above a temperature threshold may thereby indicate escape of athermal plume from a hood; i.e., a loss of capture and containment dueto the thermal plume rising in front of the external edge of the hood.As such a loss of containment is approached, the hot buffer zone tendsto grow from deep within the recess until it breaches the capture zone.This growth of the buffer zone can be indicated in precisely the sameway: by imaging a predefined field of view and recognizing the sizeand/or shape of the hot zone (the latter being defined as a zone inwhich the imaged temperature exceeds a predefined threshold). This isdiscussed further below.

The movement of a worker, the image of the food being cooked, thepresence of smoke at particular locations (such as escape of containmentat the edge of the hood), the temperature of air near the hood or withinthe canopy recess, the proximity of a worker, etc. may all be combinedto form a classification input-vector from which a condition (e.g.,percentage of full-load) classification may be derived. Algorithmic,rule-based methods may be used. Bayesian networks or neural networktechniques may be used. Alternatively, just one sensory indicator ofload may be used to determine the current load. For example, a gas rateflow sensor for a gas grill could provide the single input signal. Manypossibilities are available with current sensor, machine-classification,and control technologies.

Referring to FIG. 42, various camera angles may be employed in aload-classifier that employs optical or IR images. For example, a camera982 is positioned to image a side view of a canopy 972, range, 984, anda work area between and adjacent them. Referring also to FIGS. 43A-43Cand 44, in an IR-based camera, this side view can image a hot zone whosesize and shape are dependent on effluent load (which includes heat) andexhaust rate. FIG. 45 is a Schlerian image, but the shape of the hotplume is essentially the same as what would be provided by a thermalcamera. As the exhaust rate falls below that necessary to providecapture and containment, a hot zone image provided by the camera 982would expand progressively as illustrated in the series of FIGS.43A-43C. The hot zone changes from one associated with adequate captureand containment 990, to one on the verge of breaching 992, to one wherecapture and containment has been lost 994. The changes in the images,the rate of change of images, and the history of change of the imagesmay be employed in a control system as described to insure that captureand containment is maintained.

Referring now to FIG. 44, other camera angle views such as provided bycamera 980 may provide more information about the particular location ofthe exhaust rate deficit along the canopy 972 edge 1003. Illustrated inFIG. 44 is an oblique view of a canopy and plume 1002 showing aspillover 1001 over an edge 1003 near an end of the canopy. This imagemay be used to provide an adjustment to exhaust flow rate favoring theportion of the canopy 972 close to an end thereof, as illustrated. Theability to detect spillover and its position along the edge 1003 may beobtained by positioning a camera 986 looking downwardly so that itcaptures the entire front edge 988/1003. By taking multiple images, suchas provided by cameras 974, 980, 982, and 976, it is possible to comparethe shape of the three dimensional plume to determine an imminent spill.Thermal plumes have a characteristic waist 1005 that results from theincrease in velocity and the draw of cooler air as they rise. This waistbegins to bulge at the top as capture competency is lost. Again, thespillover can be detected as a three-dimensional model based ontemperature or opacity.

The model or two-dimensional image(s) may be graded or thresholded. Theimage resolution need not be high since the structures are highlyrepeatable and their variability quite distinct. Thus, a relativelyinexpensive imaging device may be employed with a small number ofpixels. The classification process must include unrecognized classes andbe capable of indicating same. For example, if the view of a camera isoccasionally obstructed, the image processing process should be capableof recognizing the absence of an expected image and responding to it.Images that change suddenly or do not belong to a recognized plume shapemay be classified as a bad image. The response to a bad image may be toignore it or alternatively to ramp the exhaust rate to a design maximumuntil a recognized image is acquired again. Fiducial marks or particularfeatures of the exhaust or cooking equipment may be employed to helpdetermine if the camera view is obstructed. The lack of such features orfiducials in the image may indicate the loss of the image.

Activity can be indicated by live camera images, IR and optical. Forexample, the presence of an operator near the working area of a cookingappliance may be used as a signal indicating that the cooking load isincreased. The particular activities in which the operator is engagedare likely to be highly repeatable events and readily classifiable byvideo classification methods as a result. For example, a particularstage of cooking may be characterized by the laying out of many piecesof meat on a hot grill. The movement of a worker's arms over the hotgrill placing the meat is an activity that may be readily classifiedsince it has distinct characteristics that distinguish it from otherbackground activities such as cleaning or walking around the grill.Classifying the event of placing the meat on a grill may trigger a timerto anticipate when the load reaches a maximum.

Neural networks may be trained to classify the conditions in a kitchenusing neural network techniques. The inputs from multiple devices may becombined to form a vector. The following are possible vectors.

1. Cameras

a) Thresholded image (reduce to 1-bit map; all temperatures (radiative)or light levels above a threshold are one color and all temperatures orlight levels another color. Process image to identify contiguous domainsand form an area-number histogram by counting the number of domainsfalling within each of series of size ranges. The histogram valuesdefine a vector. The contiguous domains can be further processed todefine feature points and their relationship mapped to a vector in amanner similar to optical character recognition techniques.

b) Thresholded image may be calibrated to provide high sensitivity tosmoke or the range of radiative temperatures associated with a thermalplume characteristic of the cooking appliance. The image processing maybe tuned to recognize and distinguish shapes characteristic of thermalplumes for the cooking processes being monitored. The output vector inthis case would be a characterization of the particular plume state.

c) Camera may simply band-pass a color, luminosity, or radiativetemperature range and cumulate the total of the image corresponding tothat passed signal. This would be scalar. This could be done for a quadtree where the total band-passed image area for each quadrant of theimage is passed as a component vector and this could be done down tomultiple levels of a quad tree.

d) Spot temperatures of food and empty areas on a grill or otherappliance may be used to predict the load. These may be derived from asingle IR image and processed to report the total area, averagetemperature, or other lump parameters predictive of the load.

2. Opacity Sensor

a) Opacity may be monitored between two points to detect when a plume isswelling. For example, an opacity sensor may be positioned near theinside of the edge 1003 of the canopy 972 and the opacity at that pointindicated.

b) The opacity near multiple points may be monitored and provided as asingle vector from which it is possible to deduce the scale ofturbulence induced by the thermal plume. (The opacity would be expectedto vary over time at different locations along the edge in response tothree-dimensional turbulent gusts giving rise to temporal and spatialvariability in opacity that can be resolved using multiple opacitysignals spaced apart and monitored synchronously.)

3. Audio

a) A simple frequency profile may be resolved into a histogram whosevalues correspond to the sound power in each of a series of ranges ofaudio frequency. The ranges need not be adjacent; they can amount todiscrete band pass filters. Depending on the particular cooking process,the sound of frying, grilling meat, operator activity, etc. can makecharacteristic profiles.

b) A sound-signature classifier may be employed to add the temporalcomponent to the sound classification. Depending on the type of loadbeing monitored, certain audio signatures may be present and recognizedusing technology as employed in voice recognition. For example, thesound of a switch being turned on, the sounds of a spatula being used ona grill, etc. are discrete audio events that have temporal signaturesthat are characteristic to them.

4. Temperature

a) Sensors placed at various locations may each provide components of avector.

b) Sensors may be arrayed to provide a signal indicative of a spatialtemperature profile which can be characterized by a more compact set ofnumbers than simply the whole series of temperatures. For example, thesharpest increases of temperature along respective dimensions may bereported to indicate the location of respective boundaries of thethermal plume 1003.

5. Proximity

a) The presence of food or other workpieces whose presence is predictiveof load, may be sensed. The proximity sensor may be provided as a singlesignal or multiple signals may provided from multiple sensors.Alternatively, the distance of the object may be sensed using aproximity sensor. For example, something that grows while it is heatedcould indicate a stage of a varying load.

b) The presence of an operator and the duration of the operator'spresence may be used to signal the load.

6. Motion

a) The movement of a worker, tools, and/or workpieces may be predictiveof the load.

Referring now to FIGS. 46 and 47, a great variety of different kinds ofactuators may be employed to operate the various flow control devicesdescribed above. Preferably, designs which are tolerant of greasedeposition from the effluent. A couple of embodiments are shown toillustrate the range of possibilities, but these by no means are theseintended to represent an exhaustive range. The prior art relating tohermetic seals, motor and actuator seals, high temperature, highcorrosion environments, etc. are rich with candidate devices that may beemployed. In FIG. 46 a lever formed by a first arm 1017 and a second arm1018 connected through a top wall 1019 of a canopy. The top wall iscorrugated to allow it to flex so that when an actuator 1013 pushes thefirst arm 1017 upwardly, the second arm 1018 moves downwardly actuatinga blind mechanism 1010. The embodiment of FIG. 46 thereby provides ahermetic seal between the linear actuator 1013 and the blind mechanism1010, which provides flow control. In FIG. 47, another actuatorembodiment has a motor and cam 1021 that are mounted externally from thecanopy recess 1012 which moves a blind mechanism 1022 through a seal1030 with a bellows 1022 and pushrod 1032. Again the sensitivemechanisms are isolated outside the canopy recess 1012. Many suchmechanisms may be employed and a comprehensive discussion of them is notnecessary since many suitable mechanisms are described in the machinemechanism prior art.

Referring now to FIG. 48A, a scroll shaped module 1130 has an inlet 1132through which air is admitted as indicated by arrows 1120, 1110 and 115.The admitted air swirls as indicated by helical arrows 1117 and 1110 andexits as indicated by arrows 1125. The helical motion is caused by thefact that the entry point 1132 is at a tangent to the cylindrical space1131 defined by the scroll shaped module 1130. The entry point 1132 is agap between an inside distal edge 1136 and an outside distal edge 1137defined by the scroll shape of the scroll shaped module 1130 and can beincreased and reduced in width by flexing the scroll shaped module 1130.

Referring to FIG. 48B, the scroll shaped module's 1130 are connected toeach other to form a filter cartridge 1140. The outside distal edge 1137of each module 1130 is connected to a middle portion 1138 of an adjacentmodule 1130 (except for a last module 1130′. Referring to FIGS. 49 and50, the modules 1130 may be supported in any of a number of ways so thatwhen they are drawn apart (as indicated by arrows 1171) as illustratedin FIG. 49, the inlet 1132 expands and the resistance to the inflow ofair is reduced. When the modules 1130 are squeezed together as indicatedin FIG. 50 (the force being as indicated by arrows 11, 72), the inlet1132 contracts and resistance to the inflow of air increases. As aresult, the bank of cartridges 1147 forms a combination filter and flowthrottling device.

Referring to FIGS. 51 and 52, a support mechanism with a back plate 1180and L-shaped lower braces 1195 support scroll-shaped modules 1130 bytongues 1148 on each module. The latter fit into channels 1147 formed inthe edges of back plate 1180. A sliding L-shaped seal member 1185 isslidably attached to one of the L-shaped lower braces 1195 and movedrelative to the back plate 1180 and lower braces 1195 to squeeze andexpand the scroll-shaped modules 1130. A tongue 1186 of one of theL-shaped lower braces 1185 is elongated to serve as a seal when theentire device is placed in an exhaust vent.

Referring to FIGS. 53 and 54, in an embodiment that is similar to theprevious embodiments, a set of scroll shaped modules 1270 have exits1255 in the center thereof. Thus, functionally, they are like themodules 1230 of the previous embodiments except that their outlets aretoward the middle of the filter device 1299 rather than along its edges.As in the previous embodiment, the air enters tangentially as indicatedby arrows 1265 and swirls in a helical motion until it exits asindicated by arrows 1255. Because the air does not need to exit thesides, side panels 1285 may be incorporated in a support structure 1225.A single opening 1220 may be formed in the back (downstream face) of thesupport structure for air to exit. A similar configuration 1235 to thatdescribed in connection with the embodiment of FIG. 51 may be used tocompress and expand the modules 1270.

FIG. 55 is a side view illustration of a canopy style hood 61 withadjustable side skirts 2105 according to a first inventive embodiment.Fumes 2035 rise from a cooking appliance 2041 into a suction zone of thehood 2026. The fumes are drawn, along with air from the surroundingconditioned space 2036 the hood 61 occupies, through exhaust vents andgrease filters connected to a plenum, the combination indicated at 2021.Suction is provided by an exhaust fan (not shown in the present drawing)connected to draw through an exhaust duct collar 2011. An exhaust stream2015 is then forced away from the occupied space.

At one or more sides of the exhaust hood 61 are movable side skirts 2105which may be raised or lowered by means of a manual or motor drive 2135.The manual or motor drive 2135 rotates a shaft 2115 which spools andunspools a pair of support lines or straps 2130 to raise and lower theside skirts 105. The side skirts 2061 and spool 2125, as well asbearings 2120 and the wires 2130, may be hidden inside a housing 2116with an open bottom 2117. In a preferred embodiment, the manual or motordrive 2135 is a motor drive controlled by a controller 2121 whichcontrols the position of the side skirts 2105.

Although the above and other embodiments of the invention describedbelow are discussed in terms of a kitchen application, it will bereadily apparent to those of skill in the art that the same devices andfeatures may be applied in other contexts. For example, industrialbuildings such as factories frequently contain large numbers of exhausthoods which exhaust fumes in a manner that are very similar to whatobtains in a commercial kitchen environment. It should be apparent fromthe present specification how minor adjustments, such as raising orlowering the hood, adjusting proportions using conventional designcriteria, and other such changes can be used to adapt the invention toother applications. The inventor(s) of the instant patent applicationconsider these to be well within the scope of the claims below unlessexplicitly excluded.

FIG. 56 is a schematic illustration of a control system for theembodiment of FIG. 55 as well as other embodiments. The controller 2121may control the side skirts automatically in response to incipientbreach, for example, as described in the US patent application, “Deviceand Method for Controlling/Balancing Fluid Flow-Volume Rate in FlowChannels,” incorporated by reference above. To that end, an incipientbreach sensor 2122 may be mounted near a point where fumes may escapedue to a failure of capture and containment. Examples of sensors thatmay be employed in that capacity are discussed below and includehumidity, temperature, chemical, flow, and opacity sensors.

Another sensor input that may be used to control the position of theside skirts 2105 is one that indicates a current load 2124. For example,a temperature sensor within the hood 61, a fuel flow indicator, or CO orCO2 monitor within the hood may indicate the load. When either ofincipient breach or current load indicates a failure or threat to fullcapture and containment, the side skirts 2105 may be lowered. This maybe done in a progressive manner in proportion to the load. In the caseof incipient breach, it may be done by means of an integral of thedirect signal from the incipient breach sensor 2122. Of course, any ofthe above sensors (or others discussed below) may be used in combinationto provide greater control, as well as individually.

A draft sensor 2123 such as a velocimeter or low level pressure sensoror other changes that may indicate cross currents that can disrupt theflow of fumes into the hood. These are precisely the conditions thatside skirts 2105 are particularly adapted to control. Suitabletransducers are known such as those used for making low level velocitiesand pressures. These may be located near the hood 61 to give a generalindication of cross-currents. When cross-currents appear, the sideskirts 2105 may be lowered. Preferably the signals or the controller2121 is operative to provide a stable output control signal as byintegrating the input signal or by other means for preventing rapidcycling, which would be unsuitable for the raising and lowering of theside skirts 2105.

The controller 2121 may also control the side skirts 2105 by time ofday. For example, the skirts 2105 may be lowered during warm-up periodswhen a grill is being heated up in preparation for an expected lunchtimepeak load. The controller 2121 may also control an exhaust fan 2136 tocontrol an exhaust flow rate in addition to controlling the side skirts2105 so that during periods when unhindered access to a fume source,such as a grill, is required, the side skirts 2105 may be raised and theexhaust flow may be increased to compensate for the loss of protectionotherwise offered by the side skirts 2105. The controller may beconfigured to execute an empirical algorithm that trades off the sideskirt 2105 elevation against exhaust flow rate. Alternatively, sideskirt 2105 elevation and exhaust rate may be controlled in amaster-slave manner where one variable is established, such as the sideskirt 2105 elevation in response to time of day, and exhaust rate iscontrolled in response to one or a mix of the other sensors 2124, 2123,2127, and/or 2122.

FIG. 57 is a side view illustration of a backshelf hood 2168 with a firesafety gap 2166 and movable side skirts 2172 and a movable back skirt2188. The side skirts 2172 may be one or both sides and may be manuallymoved or automatically driven as discussed above with reference to FIGS.55 and 56. The movable back skirt 2188 is located behind the appliance2180 and is raised to block the movement of fumes due to cross drafts.The back skirt amy also be attached to the hood 2168 and lowered intoposition. Note that the back skirt 2188 is shown in a partly extendedposition and may be extended variable amounts depending on the degree ofshielding required.

Note that any of the skirts discussed above and below may be configuredbased on a variety of known mechanical devices. For example, a skirt mayhinged and pivoted into position. It may be have multiple segments suchthat is unfolds or unrolls as a roller door for example as does a metalrolling garage door.

FIG. 58 is a side view illustration of a canopy style hood 62 withadjustable side skirts 2210 according to another inventive embodiment.The side skirts 2210 may be manually or automatically movable. There maybe two, one at either of two ends of the hood 62 or there may be more orless on adjacent sides of the hood 62, such as a back side 2216. In somesituations where most of the access required to the appliances can beaccommodated on a front side 2217 of the hood 62, it may be feasible tolower a rear skirt 218.

Note that it is unnecessary to discuss the location and type of drivesto be used and the precise details of manual and automatic skirtsbecause they are well within the ken of machine design. For the samereason, as here, examples of suitable drive mechanisms are not repeatedin the drawings.

Also shown in FIG. 58 is a suitable location for one or more proximitycontrol sensors 2230 that be used in the present or other embodiments.Proximity sensors may be used to give an indication of whether access toa corresponding side of the appliance 41 is required, in a manner notunlike that of an automatic door of a public building. One or moreproximity sensors 2230 may be used to raise and lower the side skirts.

As taught in U.S. Pat. No. 6,851,421 for “Exhaust Hood with Air Curtainto Enhance Capture and Containment,” incorporated by reference above, avirtual barrier may be generated to help block cross-drafts by means ofa curtain jet located at an edge of the hood. FIG. 59 is a figurativerepresentation of a combination of horizontal 2235 and vertical 2345jets to be generated at the edge 2340 and 2355 of a hood according to aninventive embodiment which has been shown by experiment to beadvantageous in terms minimizing the exhaust flow required to obtainfull capture and containment. In a preferred configuration, thehorizontal and vertical jets are made by forming holes in a plenum, forexample holes of about 3-6 mm diameter with a regular spacing so thatthe individual jets coalesce some distance away from the openings toform a single planar jet. The initial velocities of the horizontal jetsare preferably between 2 and 3.5 times the initial velocities of thevertical jets, the initial velocity in this case being the point atwhich individual jets coalesce into a single planar jet.

FIG. 60 is a figurative illustration of a plenum 2310 configured togenerate the vertical 2325 and horizontal 2330 jets with diagonalhorizontal jets 2315 at ends of the plenum 2310 according to aninventive embodiment. Referring momentarily to FIG. 61, most hoods 2307have an exhaust vent portion 2306 (such as the plenum, filter, ventcombination indicated at 2021 in FIG. 55) within the hood 2307 recessthat is centrally located so that even if the hood has a large aspectratio, at the ends, horizontal jets 2309 (2330 in FIG. 7A) are moreeffective at capturing exhaust if they are directed toward the center ofthe hood near the ends 2308 of the long sides 2302. Thus, in a preferredconfiguration of the plenum 2310, the ends 2325 of the plenum have anangled structure 2320 to project the horizontal jets diagonally inwardlyas indicated at 2315.

FIGS. 62A and 62B illustrate the position of the plenum 2310 of FIG. 7Aas would be installed in a wall-type (backshelf) hood 2370 as well as acombination of the horizontal and vertical jets with side skirts 2365according to another inventive embodiment. This illustration shows howthe plenum 210 of FIG. 7B may be mounted in a backshelf hood 2370. Inaddition, the figure shows the combination of the vertical andhorizontal jet and the side skirts 2365. In such a combination, thevelocity of the vertical and horizontal jets may be reduced when theside skirts 2365 are lowered and increased when the side skirts areraised. Note that although not shown in an individual drawing, the samecontrol feature may be applied to horizontal-only jets and vertical-onlyjets which are discussed in “Exhaust Hood with Air Curtain to EnhanceCapture and Containment,” incorporated by reference above. FIG. 62Ashows the side skirts 2365 in a lowered position and FIG. 62B shows theside skirts 2365 in a raised position. Note that the plenum 2365 may bemade integral to the hood and also that a similar mounting may beprovided for canopy style hoods. FIG. 62B also shows an alternativeplenum configuration 2311 with a straight return 2385 on one side whichgenerates vertical 2380 and horizontal 2395 jets along a side of thehood 2370. The return leg 2385 although shown on one end only may beused on both ends and is also applicable canopy style hoods with amirror-symmetrical arrangement around the wall (not shown) to which thebackshelf embodiment is referred.

FIGS. 63A-63C illustrate various ways of wrapping a series of horizontaljets around a corner to avoid end effects according to inventiveembodiment(s). These alternative arrangements may be provided by shapinga suitable plenum as indicated by the respective profile 2405, 2410,2415. Directional orifices may be created to direct flow inwardly at acorner without introducing a beveled portion 2415A or curved portion2410A as indicated by arrows 2420. FIG. 9D illustrates a way of creatinga directional orifice in a plenum 2450 to direct a small jet 2451 at anangle with respect to the wall of the plenum 2450. This may done bywarping the wall of the plenum 2450 as indicated or by other means asdisclosed in the references incorporated herein.

FIG. 64A illustrates a canopy-style hood 2500 with vertical jets 2550and a configuration that provides a vortical flow pattern 2545 that issubject to an end effects problem. The end effects problem is that wherethe vortices meet in corners, the flow vertical flow pattern isdisrupted. As discussed in “Exhaust Hood with Air Curtain to EnhanceCapture and Containment,” incorporated by reference above, the vorticalflow pattern 2545 works with the air curtain 2550 to help ensure thatfluctuating fume loads can be contained by a low average exhaust rate.But the vortex cannot make sharp right-angle bends so the quasi-stableflow is disrupted at the corners of the hood.

FIGS. 664B and 64C illustrate configurations of a canopy hood thatreduce or eliminate the end effect problem of the configuration of FIG.64A. Referring to FIGS. 64B and 64C, a round hood 2570 or one withrounded corners 2576 reduces the three-dimensional effects that canbreak down the stable vortex flow 2545. In either shape, a toroidalvortex may be established in a curved recess 2585 or 2590 with thevertical jets following the rounded edge of the hood. Thus the sectionview of FIG. 64A would roughly representative of any arbitrary slicethrough the hoods 2576, 2570 shown in plan view in FIGS. 64B and 64C.

The figures also illustrate filter banks 2580 and 2595. It may beimpractical to make the filter banks 2580 and 2595 rounded, but they maybe piecewise rounded as shown. Thus filter-holding plenum portions 2581may be rectangular and joined by angled plenum portions 2582.

FIG. 64C illustrates a configuration of a canopy hood 615 that reducesthe end effect problem of the configuration of FIG. 10 by supporting thecanopy using columns 5610 at the corners that are shaped to eliminateinteractions at the ends of the straight portions 5620 of the hood 5615.Vertical jets 5650 do not wrap around the hood 5615 and neither does theinternal vortex (not illustrated) since there are separate vorticesalong each edge bounded by the columns 5610.

FIG. 65A illustrates a hood configuration with a sensor that usesincipient breach control to minimize flow volume while providing captureand containment. Incipient breach control is discussed in “Device andMethod for Controlling/Balancing Fluid Flow-Volume Rate in FlowChannels,” incorporated by reference above. Briefly, when fumes 5725rise from a source appliance 5711, and there is a lack of sufficientexhaust flow or there is a cross-draft, part of the fumes may escape asindicated by arrow 5720. A sensor located at 5715 or nearby position maydetect the temperature, density, or other detectable feature of thefumes to indicate the breach. The indication may be used by a controllerto control exhaust flow as discussed in the above patent or others suchas U.S. Pat. No. 6,170,480 entitled “Commerical Kitchen Exhaust System,”which is hereby incorporated by reference as if fully set forth hereinin its entirety.

Various sensors may be used including optical, temperature, opacity,audio, and flow rate sensor in the present context. It is also proposedthat chemical sensors such as carbon monoxide, carbon dioxide, andhumidity may be used for breach detection. In addition, as shown in FIG.65B, an interferometric sensor may also be employed to detect anassociated change, or fluctuation, in index of refraction due to escapeof fumes.

Referring to FIG. 65B, a coherent light source 825 such as a laser diodeemits a beam that is split by a beam splitter 5830 to form two beamsthat are incident on a photo-detector 5835. A reference beam 5831travels directly to the detector 5835. A sample beam 5842 is guided bymirrors 5840 to a sample path 5860 that is open to the flow of ambientair or fumes. The reference and sample beams 5831 and 5842 interfere inthe beam splitter, affecting the intensity of the light falling on thedetector 5835. The composition and temperature of the fumes createsfluctuations in the effective path length of the sample path 5860 due toa fluctuating field of varying index of refraction. This in turn causesthe phase difference between the reference 5831 and sample 5860 beams tovary causing a variation in intensity at the detector 5835.

The direct output of the detector 5835 may be passed through a bandpassfilter 5800, an integrator 5805, and a slicer (threshold detector) 5810to provide a suitable output signal. The reason a bandpass filter may beuseful is to eliminate slowly varying components that could not be aresult of a fumes such as a person leaning against the detector, as wellas changes too rapid to be characteristic of the turbulent flow fieldassociated with a thermal plume or draft, such as motor vibrations. Anintegrator ensures that the momentary transients do not create falsesignals and the slicer provides a threshold level.

Referring to FIG. 65C, an alternative embodiment of a detector uses adirectional coupler 2630A instead of a beam splitter as in the previousembodiment. Rather than mirrors, a waveguide 2664 is used to form asample path 2660A. A light source 2625 sends light into the directioncoupler 2630A which is split with one component going to the detector2635 and the other passing through the sample path 2660A and back to thedirection coupler 2630A. Fluctuations in phase of the return light fromthe sample path 2660A causes variations in the intensity incident on thedetector 2635 as in the previous embodiment.

Preferably, the interferometric detector should allow gases to passthrough the measurement beam without being affected unduly by viscousforces. If the sample path is confined in a narrow channel, viscousforces will dominate and the detector will be slow to respond. Also,from a practical standpoint, filtering slowly varying electrical signalsmay be more difficult. Also, if the sample path is too long the signalmight be diminished due to an averaging effect. These effect of theseconsiderations vary with the application. It may also be preferable forthe gap to be longer than the length scale of the temperature (orspecies, since the fumes may be mixed with surrounding air) fluctuationsto provide a distinct signature for the signal if the gap wouldsubstantially impede the flow. Otherwise, the transport of temperatureand species through the sample beam would be governed primarily bymolecular diffusion making the variations slow, for example, if thesample beam were only exposed in a narrow opening. However, in someapplications of a detector this may be desirable, but such applicationsare likely removed from typical commercial kitchen application.Referring to FIG. 65D, an eddy is figuratively shown at 3900. Thestructure of the detector may provide a space 3918 (i.e., a sample gap3918) that is large relative to the smallest substantial turbulent scaleas indicated at 3912. Alternatively, the structure of the detector maybe smaller than the smallest turbulent scale, but thin and short asindicated at 3914 in which case viscous forces may not impede greatlythe variation of the constituent gases in the sample path 3910 due toturbulent convection. As is known in the art, the speed of flow, forforced convection, and the temperature differences, for naturalconvection, determine how small the smallest turbulent eddies. Highturbulent energy drives the momentum effects toward smaller scalesbefore the turbulent energy is dissipated in viscous friction. Lowerturbulent energy will result in larger minimum turbulent scales. Notethat an interferometric detector may detect fluctuatations even when thesample gap 3918 is smaller than the smallest turbulent eddies, thoughthe effect registered may not be as rapid or the fluctations as extremeowing to the species or temperature diffusion transport required.

Note that another alternative for measuring fluctuations in temperature,species, and or flow is a hot film or hot wire anemometer. Such devices,as is known, can have extremely sensitive response times. As is alsoknown, they respond to thermal diffusivity and heat transfercoefficient, which change with species, as well as temperature andvelocity, all of which fluctuate in a fume driven or fume-filledturbulent flow field.

FIG. 66 illustrates a combination make-up air discharge register/hoodcombination 2787 with a control mechanism 2769 and 2770 for apportioningflow between room-mixing discharge 2786 and short-circuit discharge 2776flows. A hood 2774 has a recess through which fumes 2794 flow and areexhausted by an exhaust fan 2779, usually located on the top of aventilated structure. A make-up air unit 2745 replaces the exhausted airby blowing it into a supply duct 2780 which vents to a combinationplenum that feeds a mixed air supply register 2786 and a short-circuitsupply register 2776. The fresh air supplied by the make-up air unit2745 is apportioned between the mixed air supply register 2786 and ashort-circuit supply register 2776 by a damper 2770 whose position isdetermined by a motor 2765 which is in turn controlled by a controller2769.

When air is principally fed to the short-circuit supply register 2776,it helps to provide most of the air that is drawn into the hood 2787along with the fumes and exhausted. Short-circuit supply of make-up airis believed by some to offer certain efficiency advantages. When theoutside air is at a temperature that is within the comfort zone, or whenits enthalpy is lower in the cooling season or higher in the heatingseason, most of the make-up air should be directed by the controller2769 into the occupied space through the mixed air supply register 2786.When the outside air does not have an enthalpy that is useful forspace-conditioning, the controller 2769 should cause the make-up air tobe vented through the short-circuit supply register 2776.

FIG. 67 illustrates a combination make-up air discharge register andhood combination with a control mechanism for apportioning flow betweenroom-mixing discharge and a direct discharge into the exhaust zone ofthe hood from either outdoor air, transfer air from another conditionedspace, or a mixture thereof. A blower 2797 brings in transfer air, whichmay be used to supply some of the make-up air requirement and provide apositive enthalpy contribution to the heating or cooling load. Thestaleness of transfer air brought into the heavily ventilatedenvironment of a kitchen is offset by the total volume of make-up(fresh) air that is required to be delivered. Sensors on the outside2775, the occupied space 2730, in the transfer air stream and/or thespace from which transfer air is drawn 2731 may be provided to indicatethe conditions of the source air streams. A mixing box 2746 may be usedto provide an appropriate ratio of transfer air and fresh air. The ratiowill depend on the exhaust requirements of the occupied space 2796.Control of the damper 2770 is as discussed with reference to FIG. 66.

FIGS. 68A, 68B, and 70 illustrate drop-down skirts that can be manuallyswung out of the way and permitted to drop into place after a the lapseof a watchdog timer under control of a controller shown in FIG. 69.FIGS. 68A and 68B are side views of a drop-down skirt 915 that pivotsfrom a hinge 905 from a magnetically suspended position over a cookingdevice 930. In 68A, the skrit or skirts 915 is/are shown in a raisedposition and in FIG. 68B in a dropped position. A magneticholder/release mechanism 935, which may include an electromagnet orpermanent magnet, holds the skirt panel 915 in position out of the wayof an area above a fume source 930. The skirts 915 may be released afterbeing moved up and engaged by the magnetic holder/release mechanism 935,after a period of time by a controller 960. The controller 960 may beconnected to a timer 970, a proximity sensor 925, and the magneticholder/release mechanism 935. The proximity sensor 925 may be one suchas used to activate automatic doors. If nothing is within view of theproximity sensor after the lapse of a certain time, the controller mayrelease the skirt 915. When released by the magnetic holder/releasemechanism 935, the skirt 915 falls into the position of FIG. 68B toblock drafts. Preferably, as shown in the front view of FIG. 70, thereare multiple skirts 915 separated by gaps 916. A passing worker may scanthe area behind the skirts 915 even though they are down if the workermoves at least partly parallel to the plane of the skirts 915. In anembodiment, the magnetic holder/release mechanism 935 may combined withthe controller 960, the timer 970, and the proximity sensor 925 in aunitary device.

Note that although in the above embodiments, the discussion is primarilyrelated to the flow of air, it is clear that principles of the inventionare applicable to any fluid. Also note that instead of proximitysensors, the skirt release mechanisms described may be actuated by videocameras linked to controllers configured or trained to recognize withevents or scenes. The very simplest of controller configurations may beprovided. where a blob larger than a particular size appears ordisappears within brief interval in a scene or a scene remainsstationary for a given interval. An example of a control flow isillustrated in FIG. 73. A controller detects the latching of the skirtas step S900 and starts a watchdog timer at step S905. Control thenloops through S910 and S915 as long as scene changes are detected.Again, simple blob analysis is sufficient to determine changes in ascene. Here we assume the camera is directed view the scene in front ofthe hood so that if a work is present and working, scene changes willcontinually be detected. If no scene changes are detected until thetimer expires (step S915), then the skirt is released at step S920 andcontrol returns to step S900 where the controller waits for the skirt tobe latched. A similar control algorithm may be used to control theautomatic lowering and raising of skirts in the embodiments of FIGS.55-58, discussed above. Instead of releasing the skirt, the skirt wouldbe extended into a shielding position and instead of waiting for theskirt to be latched, the a scene change would be detected and the skirtautomatically retracted.

Referring to FIG. 71, multiple sample gaps, such as the two indicated at4915 may be linked together under in a common light path by a lightguide 4900 and a single directional couple 4830 or equivalent device. Asin prior embodiments, a light source 4835 and detector 4825 areconnected by a directional coupler 4830 with focusing optics 4862 andone or more linking light guides 4905 to provide any number of samplepaths. FIG. 72A shows a hood edge 4920 with multiple individual sampledevices 4871 which conform to any of the descriptions above linked to acommon controller. Although parallel connections are illustrated, serialconnections of either fiber or conductor may be provided depending onthe configuration.

Although in the embodiments described above and elsewhere in thespecification, real-time control is described, it is recognized thatsome of the benefits of the invention may be achieved without real-timecontrol. For example, the flow control device 120 may be set manually orperiodically, but at intervals to provide the local load control withoutthe benefit of real-time automatic control.

1. A detector for detecting fumes escaping from an exhaust hood,comprising: an optical interferometer configured to send light through asample path and create an interference pattern with respect to areference beam in the vicinity of an exhaust hood; an optical detectorconfigured to detect fluctuations in said pattern; a controllerconfigured to detect said fluctuations and respond to a pattern thereofby generating a control signal for controlling a mechanism forcontrolling a shield that at least partly covers an access of saidexhaust hood.